PENTAGONS, HEPTAGONS AND NEGATIVE CURVATURE IN GRAPHITE MICROTUBULE GROWTH
PENTAGONS, HEPTAGONS AND NEGATIVE CURVATURE IN GRAPHITE MICROTUBULE GROWTH
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DOI：
10.1038/356776a0
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发表时间：
1992-04-30
期刊：
影响因子：
64.8
通讯作者：
ANDO, Y
中科院分区：
文献类型：
--
作者：
IIJIMA, S;ICHIHASHI, T;ANDO, Y
富勒烯的标准碳弧合成也会产生螺旋结构的石墨微管。在大多数情况下，圆柱形管被多面体盖住，有些在盖住之前先被改造成锥形。在这里，我们展示了另一种生长形态的透射电子显微镜图像，其中锥状生长通过引入诱导负曲率的缺陷而转变为圆柱形生长。我们认为六边形网络中导致负曲率的缺陷可能是一个单一的七方环。Terrones和Mackay最近提出了三维、开放的负弯曲石墨结构。我们更广泛地讨论了五角形和七角形对这些小管生长形态的影响，以及管闭合对五角形缺陷数量的限制。
THE standard carbon-arc synthesis for fullerenes also produces graphitic microtubules with helical structures 1. In most cases the cylindrical tubes are closed by polyhedral caps, some being first transformed into a conical shape before closure 2. Here we present images from transmission electron microscopy of a further kind of growth morphology, in which cone-like growth is transformed into cylindrical growth by the incorporation of a defect that induces negative curvature. We suggest that the defect in the hexagonal network responsible for negative curvature may be a single heptagonal ring. Three-dimensional, open negatively curved graphitic structures have been proposed recently by Terrones and Mackay 3. We discuss more generally the effect of pentagons and heptagons on the growth morphologies of these tubules, and the constraints on the number of pentagonal defects imposed by tube closure.